The Web novel may have been compiled to 10 volumes, but those volumes were rediculous large. Considering that what was the 8th volume was split in 2 and does not even finish the arc fully, saying that the light novel version would be finished at 10 is an under estimation.

Minimum would be for the series to end at 12 in my estimation, possibly 13 volumes. I am not aware of after story being published officially either and won't be considered likely until the main story is complete.

As @custodes already explained, there's no way the LN will end with volume 10. Other than that, Overlap mentioned that they'll keep publishing Arifureta as long as it sells. Which means there's a high chance the after stories will be published, too.

I always firmly believe in reading the Light novel version, rather than the Web Novel once you start in a format unless circumstances dictate i.e. the series gets cancelled.
This is due to the importance of an editor, allowing things to remain chronological, instead of just being a convoluted mixture of idea, which sadly the after stories are in my opinion. Heck the author has stated that they cannot even remember certain plotlines or where they belong in the timeline.

I would hold out for now, they are humorous, but I would rather wait for the slick and finalised version if and when it comes out if you have not started already. Or if you must do so, wait until the main series ends so that you are not spoiled or unhappy by any possible changes.

There's no indication that they're going to make the Afterstory a separate publication rather than just keep publishing the it as additional volumes to the main series. Plus, volume 10 isn't the last volume of the main story. It came out just last month.

No offence, but I dont actually know that :)
Thanks for pointing out about the volume, I tried searching amazon.co.jp for Arifureta 10, but found nothing, so I assumed it was not released. Now I can finally flip a table and have an outrage. Like, why are we not translating volume 10 yet? What the hell j-novel!